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Background information for Energy

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Below you will find some commonly asked questions about energy. You may also want to explore the other topics relating to our school program «The Many Faces of Energy».

What is energy?

Energy is the ability to do work, the ability to exert a force on an object to move it.

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What are the sources of energy?

What are renewable and non-renewable sources of energy?

Renewable sources of energy are those which are not exhaustible, such as solar energy, wind energy and tidal energy.

Non-renewable sources of energy can be used up or depleted; they include the fossil fuels and nuclear energy sources.

Renewable sources of energy

- energy from the Sun

Most sources of energy, with the exception of nuclear energy, are derived from the Sun, or solar radiation.

- energy from the rivers

Hydraulic or water energy results from the water cycle and can be used to run mills (water wheel or turbine) and to produce electricity, as at Churchill Falls, Newfoundland, or the Carillon Hydroelectric Power Station on the Ottawa River.

- energy from winds

Wind energy is obtained from moving air and is used in transportation, irrigation and power generation. The windmill was used for grinding grain.

- energy from the tides

Tidal energy can be harnessed and used for generating electricity, using reversible turbines such as those at Annapolis Royal, Nova Scotia.

- energy from hot springs

Geothermal energy comes from the heat within the Earth. It is used to generate electricity and for residential and commercial heating in certain locations (e.g., Iceland and Japan).

-energy from biomass

Biomass energy is solar energy that has been captured by vegetation and stored in the form of matter that can be used as fuel. For example, wood, wood chips, even garbage can be incinerated and the heat used to produce steam to heat office buildings, as in Charlottetown, Prince Edward Island.

Non-renewable sources of energy

- energy from fossil fuels

coal: Formed from land vegetation living hundreds of millions of years ago that becomes a sedimentary rock containing 60-90% carbon. In Canada, coal is found in Nova Scotia, New Brunswick, Saskatchewan, Alberta and British Columbia

petroleum: Formed from organic deposits (lipids) rich in hydrogen that become hydrocarbons under the effects of accumulated sediments and growing temperatures; it takes tens of millions of years to form. The Alberta Oil Sands produce petroleum in Canada.

natural gas: A continuation of the petroleum-making process over tens to hundreds of millions of years results in natural gas. In Canada, natural gas is produced at the Sable Offshore Energy Project off the coast of Nova Scotia

- energy from nuclear fission

Nuclear energy results from the fission, or splitting, of heavy atoms like uranium or plutonium. This atomic splitting releases energy. The CANDU reactor first used at Rolphton, Ontario, and now also used throughout Ontario, as well as in Quebec, New Brunswick and six other countries, is used to produce electricity from nuclear energy.

Energy Quest

CREST

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What is the water cycle?

Water is always in motion. It evaporates into the air in the form of water vapour. Warm air (heated by the Sun's energy) can hold more water vapour than cold air. As warm air rises from a body of water it takes a lot of water vapour with it. Sooner or later this warm, water-laden air cools, and the water vapour turns into rain. The rain falls on the Earth, flows down creeks and rivers to lakes, and eventually is either evaporated again or returns to the oceans. This water cycle is repeated over and over again.

Hydraulic energy from flowing rivers can be harnessed by dams and used to run mills (turbines); electricity can be produced by hydro-electric generating stations such as those at Gull Island in Newfoundland or the James Bay River Project in Quebec.

The process of hydraulic energy includes prime movers:

  • water wheel (the most ancient)
  • turbines (water turbines were invented in the early 19th century)

Both the water wheel and the water turbine can be seen today still in motion in historic mills.

Until the end of the 18th century, the water wheel was the principal source of motive power.

The Water Cycle

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What are potential and kinetic energy?

Potential energy

Lift a small block in the air. The block has the potential to do work by virtue of its position in the air. It possesses potential energy. The potential energy of the block is due to gravity. Other examples of potential energy are a wound spring, a taut bowstring, a stretched rubber band and an inflated balloon.

Kinetic energy

Let the block fall. The block has kinetic energy, the energy of movement as it falls, and has the ability to do work. Potential energy is converted into kinetic energy. The kinetic energy in this example is also due to the force of gravity.

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What are the different forms of energy?

Some examples of forms of energy are as follows:

  • mechanical energy - the moving force behind machinery
  • chemical energy - derived from wood, coal, oil, food, etc., all of which undergo chemical reactions to provide us with heat or sustenance
  • muscular energy - derived from the chemical energy of the food we eat
  • thermal energy - the steam in a steam engine or heat of exploding gases in a gas engine
  • light energy - plants draw their energy from sunlight by a process called photosynthesis, or photocells
  • electrical energy - associated with water power, magnets, electrical currents and combinations of these
  • nuclear energy - energy released by atoms and converted to heat and then to electrical energy

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What forms of energy are used in transportation?

Sailboat: mechanical energy (source: wind)

Walking, roller skating, cycling, canoeing: muscular energy (source: food)

Train: chemical energy (source: fossil fuels) or electrical energy

Car: chemical energy (source: fossil fuels and, in future, Ballard hydrogen fuel cells)

The most efficient means of transportation in terms of energy utilization is the bicycle. To cover one kilometre, a cyclist expends 20 to 100 times less energy than a car driver.

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What are some examples of energy transformation or conversion?

In every situation, the transformation of energy is inefficient because we are unable to harness all the energy available. It is not possible, for example, to convert the chemical energy of coal directly into electrical energy. It must first be burned in order to heat water and create steam, which then turns a turbine to produce electricity. In such a transformation, energy efficiency is reduced. Old-fashioned steam engines had an efficiency of 6 to 7%, due to heat loss from the sides of the locomotive and loss of steam and heat up the stack. Ask your students to think of other ways energy is lost.

There are various transformations of energy in a steam-driven locomotive. The chemical energy released from the burning coal is used to heat water and produce steam. The steam drives the pistons that make the wheels turn (mechanical energy). Part of the driving motion of the pistons is used to power generators that create electrical energy for heat and light. Surplus electrical energy is fed back into storage batteries, converted to chemical energy and stored to be reconverted to light and heat.

The water cycle and hydro-electric power production are other examples of energy transformation. Heat energy from the Sun evaporates the water in lakes and oceans. The water vapour collects into clouds and falls as rain. The water flows downhill and can be restrained by a dam (potential energy). It is then released (kinetic energy) to turn turbines, in the production of electricity used to perform a variety of tasks in homes and industries.

To measure the effects of energy conversion and its efficiency, the transmission and consumption of energy are also very important.

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How efficient is the transformation of energy?

The transformation of energy is never 100% efficient because we cannot usefully capture all the energy supplied by one source.

For some operations, energy conversion from one form to another may approach 100% efficiency (e.g., the conversion of mechanical energy from a generator's rotor into electrical energy is 95-99% efficient).

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What are some examples of energy transformation or conversion?

In every situation, the transformation of energy is inefficient because we are unable to harness all the energy available. It is not possible, for example, to convert the chemical energy of coal directly into electrical energy. It must first be burned in order to heat water and create steam, which then turns a turbine to produce electricity. In such a transformation, energy efficiency is reduced. Old-fashioned steam engines had an efficiency of 6 to 7%, due to heat loss from the sides of the locomotive and loss of steam and heat up the stack. Ask your students to think of other ways energy is lost.

There are various transformations of energy in a steam-driven locomotive. The chemical energy released from the burning coal is used to heat water and produce steam. The steam drives the pistons that make the wheels turn (mechanical energy). Part of the driving motion of the pistons is used to power generators that create electrical energy for heat and light. Surplus electrical energy is fed back into storage batteries, converted to chemical energy and stored to be reconverted to light and heat.

The water cycle and hydro-electric power production are other examples of energy transformation. Heat energy from the Sun evaporates the water in lakes and oceans. The water vapour collects into clouds and falls as rain. The water flows downhill and can be restrained by a dam (potential energy). It is then released (kinetic energy) to turn turbines, in the production of electricity used to perform a variety of tasks in homes and industries.

To measure the effects of energy conversion and its efficiency, the transmission and consumption of energy are also very important.

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How efficient is the transformation of energy?

The transformation of energy is never 100% efficient because we cannot usefully capture all the energy supplied by one source.

For some operations, energy conversion from one form to another may approach 100% efficiency (e.g., the conversion of mechanical energy from a generator's rotor into electrical energy is 95-99% efficient).

For most operations, however, efficiency is reduced: it is impossible, for example, to convert coal's chemical energy directly into electrical energy. The coal must first be burned to heat water and produce the steam that turns a turbine to generate electricity. Up to 80% of the fuel could be dispersed in the form of heat and noise.

All machines lose efficiency because of friction. What does friction produce? Heat and sound. What does the burning fuel produce? Heat and sound. What does the spinning turbine do to the water passing through? It slows the water and expends energy heating it. Low-grade heat and noise, therefore, account for the apparent loss of energy in transformations. Most of the heat is not usable, however, but is dispersed. Energy must be able to flow or be transferable in order to do work. It is not usable when such a transfer is no longer possible.

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What does conservation of energy mean?

Experiments on the transfer of energy were performed by the Dutch scientist Christiaan Huygens (1629-1695). He studied the effects of collisions between billiard balls and found that the sums of the kinetic energies of two billiard balls before and after collision are the same. Although one ball may slow down, the other will speed up.

Huygens concluded that, while energy may be transferred, it will not be lost. These ideas laid the ground work for a fundamental concept in physics, the Law of Conservation of Energy.

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What is the Law of Conservation of Energy?

The Law of Conservation of Energy states that energy in the universe can be neither created nor destroyed. This law was formulated in the 1840s by the German scientists Hermann von Helmholtz and Julius Robert von Mayer, and by the British scientist James Prescott Joule.

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Energy and the environment

It is impossible to collect or to consume energy without causing certain changes to the environment. The effects of recovering and using energy are far-reaching and can be seen at each stage of the energy cycle, from methods of extracting resources to the ways in which these resources are transported and used for heating, lighting, transportation and manufacturing.

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Environmental Effects of Different Sources of Energy

Petroleum

The carbon dioxide that is released in the combustion of fossil fuels, including petroleum, contributes to the greenhouse effect. Other gases released in this way may be toxic and/or carcinogenic (e.g., carbon monoxide, certain hydrocarbons, benzene). Subsequent chemical transformations of these gases produce low-altitude ozone and nitrous oxides, etc. The transportation of petroleum is hazardous to the environment, especially when tanker vessels run aground, producing massive oil spills. Research is being conducted with the aim of increasing the efficiency of petroleum and decreasing its emissions.

Coal

The gases released by the combustion of coal contribute to the greenhouse effect (carbon dioxide) and to the formation of acid rain, which damages lakes, forests, crops and buildings. There are now ways to effectively control acid gas emissions. Additional means of reducing other emissions that are dangerous to the environment, such as carbon dioxide, are now being developed. Coal recovery through open-pit mines also has a considerable impact on the environment.

Natural Gas

Currently, natural gas is the least harmful fuel in terms of the environment since it releases less carbon dioxide and other noxious gases during combustion (though it does release some CO2). The construction and presence of large pipeline networks for transport of this fuel have an impact on the immediate environment.

Nuclear energy

A problem for the environment is the production of long-life radioactive wastes, i.e. thousands of years, in the form of used-up fuel bundles and remainders of old, dismantled nuclear power stations that produce electricity for approximately 40 years. The advantage of nuclear fuel is that it requires very little space. The power from nuclear fuel the size of a volleyball would provide all the energy required by a Canadian for his or her entire life! There is no air pollution.

Hydro-electricity

A problem for the environment is the flooding of immense expanses of land that profoundly affects the ecosystems. In newly created reservoirs, chemical reactions release the mercury naturally present in the soil. Use of PCBs as an insulator in transformers, even though they were banned in the 1970s, poses a serious environmental hazard.

Wind and solar energy

Windfarms and solar batteries require space and result in visual pollution in the landscape. They are, however, a "clean" energy (no waste produced).

Geothermal energy

A problem for the environment is the potential release of gas or water containing toxic products from underground deposits. There is noise pollution (release of high-pressure steam). With the release of heat, there are considerable local climatic changes.

Biomass Energy

Misuse of plants and trees (forests, peat, etc) might locally render the soil sterile by increasing surface run-off and encouraging wind erosion. Plant combustion releases carbon dioxide into the atmosphere, contributing to global warming. Biomass energy also means reducing the quantity of plants that can absorb carbon dioxide, thereby increasing the greenhouse effect.

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